The semiconductor wafer of silicon and gallium arsenic or so is produced in a large diameter, and this wafer is cut and separated (dicing) into small pieces of the element (the semiconductor chip), then moves on to the mounting step which is the subsequent step. At this time, the semiconductor wafer is adhered on the adhesive sheet in advance and the steps of dicing, washing, drying, expanding, and pickup are carried out respectively, then it is moves on to the bonding step which is the subsequent step.
Among these steps, in order to simplify the processes of the pickup step and the bonding step, various dicing die bonding adhesive sheets which comprises both of the wafer fixing function and the die adhesive function are proposed (refer to the patent article 1). The adhesive sheet disclosed in the patent article 1 enables the so-called direct die bonding, and allows omitting the coating step of the die adhering adhesive agent. This adhesive agent includes acrylic polymer, unsaturated hydrocarbon group containing epoxy resin, and heat curing agent; and if needed, a filler such as silica may be included.
The property required against the recent semiconductor device is extremely severe. For example, in regards with the connection of the electrical parts, the surface mounting method (reflow) wherein the entire package is exposed to a high temperature which is higher than the melting point of the soldering is being carried out. Further, recently, due to the transition to the soldering which does not include lead, the mounting temperature has increased to 260° C. or so. Therefore, the stress generated inside the semiconductor package during the mounting has become larger than before, hence the chances of causing problems such as peel or package crack at the adhesive boundary have increased. Thus, in said patent article 1, as for epoxy resin, the unsaturated hydrocarbon group containing epoxy resin is used to improve the compatibility between the acrylic polymer and the epoxy resin, thereby adhesive reliability is improved.
Also, for the high density mounting, the package structure in which the chips are multiply stacked is proposed. In this package structure, not only the connection between the circuit board and the chip, but also the adhering between the chip and the chip is necessary. In the multistacked package, the chip is stacked on the chip via the adhesive layer and after curing the adhesive layer, the wire bonding is carried out, then further the stacking of the chip, curing of the adhesive layer, the wire bonding are carried out one after another, thereby the chips are stacked. However, in this method, the curing of the adhesive layer is carried out each time the chip is stacked, hence when the number of the stacked chips increases, the production steps increases, therefore the improvement of the production efficiency is in demand.
Thus, it is being examined to simultaneously cure the adhesive layer by using the long time exposure to a high temperature at the mold sealing step after all the chips are stacked after carrying out the stacking and the wire bonding while the adhesive layer is before cured or semi-cured and without carrying out the curing of the adhesive agent at the stacking of the chip. By applying such simultaneous curing, the process to carry out the curing of each adhesive layer can be omitted; thereby the productivity can be improved. However, when applying such production method, the adhesive layer is not cured or semi-cured during the wire bonding. Therefore, the chip vibrates or displaced during the wire bonding, the position of the wire may be inaccurate or the wire bonding may not be carried out. In order to solve such problem, when using the above mentioned production method, even if it is before cured, a relatively hard adhesive agent will be used. As for the means to make the adhesive agent of before curing harder, it is thought to blend a relatively large amount of the filler in the adhesive agent.
[Patent Article 1] JP Patent Application Laid Open No 2008-133330
However, it is not necessarily easy to uniformly mix the filler in the adhesive agent. If the dispersibility of the filler in the adhesive agent is bad, the appearance of the particle diameter becomes large due to the aggregation between the fillers, thereby the thickness accuracy of the adhesive layer may be lowered, or it may be the cause to lower the lamination property and the adhesiveness between the semiconductor wafers. Particularly, if the blending amount of the filler increases, the above mentioned problem becomes prominent. Also, if the filler is blended to the adhesive agent in a large amount, the blending amount of the curable component (the epoxy resin or so) decreases relatively, thereby the reliability of the adhesive layer after the curing may be lowered.
Further, even when the process to carry out simultaneous curing of the adhesive layer as mentioned in the above is used, a high temperature of 150° C. or higher is necessary during the wire bonding; thus in some case the adhesive layer was partially cured. In case of such undesirable curing, the pressure is not applied, hence when the adhesive layer is cured; the adhesive force is simply lost which leads to lowering of the adhesive strength. When the adhesive layer is partially cured, the following property to the rough surface is lowered particularly, and the adhesiveness against the circuit board surface or die pad having relatively large roughness declines significantly. Therefore, in regards with the production of the multistacked package, in order to carry out the adhesion between the circuit board and the chip securely, it was necessary to use the adhesive agent different from that of used for the adhesion between the chips; or to carry out the adhesion curing between the chip and the circuit board separately from the above mentioned simultaneous curing; which was thought as the cause of the lowering of the productivity.
Therefore, the object of the present invention is to provide an adhesive composition, and an adhesive sheet having an adhesive layer comprising said adhesive composition, and production method of a semiconductor device using said adhesive sheet; capable of uniformly mixing the filler in the adhesive layer, capable of stably carrying out wire bonding before the simultaneous curing even when the process of carrying out simultaneous curing of the adhesive layer is applied when producing the multistacked package, and exhibiting an excellent adhesive strength after the curing; further particularly capable of accomplishing high packaging reliability in the semiconductor device.